This invention relates to a catheter including an expandable member, such as a balloon, for dilatation or delivery of an endoprosthesis.
Catheters with an expandable member, such as a balloon, are used to treat body lumens that have been occluded or weakened by disease. In angioplasty, for example, a catheter is threaded through the vasculature to locate the balloon at the site of an occlusion where the balloon is inflated to dilate the lumen. To maintain the lumen in a dilated condition, a tubular endovascular prosthesis may be provided at the site. The prosthesis is placed over the balloon such that, when the balloon is inflated, the prosthesis is expanded into contact with the wall to hold the lumen open. To treat aneurysms, a graft may be provided over the balloon. The ends of the graft are attached to healthy portions of the lumen on either side of the aneurysm so that the body of the graft bridges the weakened area.
In an aspect, the invention features treating a stricture site inside the body of a patient. The site is treated by providing a system including a catheter having a proximal portion remaining outside the body and a flexible shaft that can be positioned inside the body. The shaft includes in a distal portion a selectively expandable member which can be expanded from a low profile for delivery to the site to an expanded profile for treating the site. The system also includes a strip wrapped in a helical fashion about the expandable member such that the strip is stretched when the expandable member is expanded to the expanded profile. The catheter is delivered to the site and the expandable member expanded to treat the site.
In another aspect, the invention features a system for placing an endoprosthesis at an implantation site in the body of a patient. The system includes a catheter having a proximal portion remaining outside the body and a flexible shaft that can be positioned inside the body. The shaft includes in a distal portion a selectively expandable member which can be expanded from a low profile for receiving the endoprosthesis in a compact configuration for delivery to the site and an expanded profile for implanting the prosthesis at the site. The system also includes a strip wrapped in a helical fashion about the expandable member such that the strip is stretched when the expandable member is expanded to the expanded profile.
In another aspect, the invention features a system for placing an endoprosthesis at an implantation site in the body of a patient. The system includes a catheter having a proximal portion remaining outside the body and a shaft for positioning inside the body. The shaft includes in a distal portion a selectively expandable inflatable balloon which can be expanded from a small cross-sectional profile for receiving the endoprosthesis in a compact configuration for delivery to the site and an expanded cross-sectional profile for implanting the prosthesis at the site. The system also includes an elastic strip attached to the catheter at opposite ends of the balloon and wrapped in a series of overlapping turns about the balloon such that the strip is elastically stretched when the balloon is expanded and elastically recovers when the expandable member is collapsed after implantation of the prosthesis.
Embodiments may also include one or more of the following. The strip provides greater resistance to expansion in one part of the expandable member than another part of the expandable member such that the parts expand sequentially as expansion force is increased. The central portion of the expandable member expands prior to end portions proximal and distal thereof. The distal end portion expands prior to portions proximal thereof. The strip is wrapped in a manner that the wrap angle of the helical turns varies at locations corresponding to different parts of the expandable member. The wrap angle is greater at a location corresponding to a first part of the expandable member than at a location corresponds to a second part of the expandable member to permit inflation of the first part prior the second part as expansion force is increased. The wrap angle is greater in a central portion than in portions proximal and distal thereof. The wrap angle between helical turns is greater in a distal portion than in proximal portions.
Embodiments may also include one or more of the following. The strip is wrapped in a manner that the tension of the strip varies at locations corresponding to different parts of the expandable member. The geometry of the strip varies at locations corresponding to different parts of the expandable member. The strip is wider at a location corresponding to one portion then at a location corresponding to another portion. The strip is thicker at a location corresponding to one portion then at a location corresponding to another portion. The strip is attached to the catheter shaft at a location proximal and distal of the expandable member. The strip has a relatively low friction surface facing the prosthesis and a relatively high friction surface facing the balloon. The expandable member is a fluid-inflatable balloon. The balloon is formed of a nondistendible polymer. The prosthesis is formed of polymeric material. The prosthesis includes polymeric material with metal stents at its ends. The catheter is delivered and withdrawn through an endoscope. The system further includes members extending over the ends of the prosthesis when the ends are in a compact profile condition and the members are slidable from the ends when the ends are expanded to the expandable profile.
Embodiments may include one or more of the following advantages. The helically wrapped strip can be used to vary the sequence of inflation of different portions of an expandable member, such as a balloon and an overlying prothesis, by varying the nature of the wrap about the corresponding portions to effect differing resistance to expansion force. In particular cases, the strip is wrapped in a manner that a central portion inflates prior to distal and proximal portions or in a manner that a distal portion inflates prior to more proximal portions. These inflation sequences may have particular advantages when using the system to expand a prosthesis including a highly malleable material such as PTFE or other polymer. By expansion of the central or distal portion first, the malleable graft will not be pushed off the end of the catheter, as might be the case if the proximal portion is inflated first. Nor will the prosthesis be axially compressed, as might occur if both the proximal and distal portions are inflated prior to the central portion.
In addition, the wrap may have a slippery surface compared to conventional balloon materials, such as PET, so that a polymer prosthesis is readily released from the balloon after it is expanded. (The stickiness between PET and PTFE is believed to be caused by surface tension interaction between these two smooth-surface materials or due to localized vacuum effects caused by the porous nature of the PTFE.) Further, in cases where the wrap exhibits elasticity, it may reduce the profile of the balloon upon deflation by aiding balloon refolding.
Still further features, aspects, and advantages follow.